1. Field of the Invention
The present invention relates to a semiconductor device.
2. Background of the Related Art
A semiconductor device (igniter) which controls the flow of a low-voltage current to a primary coil of an ignition coil has been known as a structural portion of an internal-combustion engine ignition device which ignites an air-fuel mixture that is introduced into a combustion chamber of a gasoline engine used in, for example, a vehicle. In recent years, a one-chip igniter in which an insulated gate bipolar transistor (IGBT) forming a switch that controls the flow of a low-voltage current to the primary coil and a circuit portion for controlling the IGBT are provided on the same chip has been known as the igniter. The one-chip igniter according to the related art has a self-separation structure in which the IGBT and an element in the circuit portion are separated from each other by a predetermined distance and can be electrically separated from each other. The structure of the one-chip igniter with the self-separation structure according to the related art will be described in the following.
FIG. 14 is a plan view illustrating the planar layout of the one-chip igniter according to the related art. FIG. 15 is a cross-sectional view illustrating a cross-sectional structure taken along the cutting line AA-AA′ of FIG. 14. As illustrated in FIGS. 14 and 15, the one-chip igniter according to the related art includes an IGBT portion 110, a circuit portion 120, and a breakdown voltage structure portion 130 which are formed in a semiconductor chip obtained by epitaxially growing an n+ buffer region 102 and an n− drift region 103 in this order on a p+ semiconductor substrate 101 and forming a plurality of p+ regions 104 diffused in a surface layer of the n− drift region 103. In FIG. 15, the plurality of p+ regions 104 are simplified and are illustrated as one p+ region 104. The IGBT portion 110 and the circuit portion 120 are arranged in parallel at the center of the chip. For example, an IGBT forming a switch of an igniter is arranged in the IGBT portion 110.
The circuit portion 120 includes a first circuit portion 121 in which an active element, such as an insulated gate field effect transistor (MOSFET), is arranged and a second circuit portion 122 which functions as a self-separation region for electrically separating the IGBT in the IGBT portion 110 from each element in the first circuit portion 121. The second circuit portion 122 is arranged with a predetermined width (a width in the direction of the cutting line AA-AA′) w0 between the IGBT portion 110 and the first circuit portion 121. As such, when the second circuit portion 122 is provided to separate the first circuit portion 121 from the IGBT portion 110, it is possible to reduce the value of the parasitic current of the IGBT in the IGBT portion 110 which flows from the IGBT portion 110 to the first circuit portion 121.
As such, when the second circuit portion 122 functions as a self-separation region, the adverse effect of the parasitic current of the IGBT in the IGBT portion 110 on each element in the first circuit portion 121 is suppressed and the surge resistance of the first circuit portion 121 is ensured. In order to effectively use the occupation area of the second circuit portion (hereinafter, referred to as a self-separation region) 122, a component which is not adversely affected by the parasitic current of the IGBT in the IGBT portion 110 among a plurality of components forming the circuit portion 120, that is, a component, such as a wiring line, an electrode pad, or a polysilicon device, which is provided over the front surface of the chip, with an oxide film interposed therebetween, and does not come into contact with a silicon portion is arranged in the self-separation region 122.
As a semiconductor device with a trench separation structure in which an IGBT portion and a circuit portion are arranged on the same chip, a device with a structure in which a deep trench is formed between an IGBT portion and a protective circuit portion and is filled with an insulator, for example, a silicon oxide film (SiO2) has been proposed (for example, see JP 2011-119542 A (Patent Document 1). As disclosed in Patent Document 1, when the trench is formed so as to reach the vicinity of a p+ collector region close to the anode, the effect of the structure is improved. This phenomenon is remarkable in a device in which a switching speed does not matter, particularly, in an engine ignition device. In addition, as the semiconductor device with the self-separation structure in which the IGBT portion and the circuit portion are arranged on the same chip, a device is proposed in which an IGBT and a control unit are substantially surrounded by a field terminal except for a narrow surface channel or a neck region (for example, see JP 9-181315 A (Patent Document 2).
However, in the one-chip igniter with the self-separation structure according to the related art, the occupation area of each component forming the circuit portion 120 can be reduced by, for example, a miniaturization technique and it is possible to reduce the area of the first circuit portion 121 according to the occupation area of the components. However, it is difficult to reduce the area of the self-separation region 122. Therefore, an invalid region in which no component is arranged and which has an area corresponding to the product of the width w0 (=about 800 μm) of the self-separation region 122 and the length of one side of the chip is generated in the circuit portion 120. That is, in the structure according to the related art, there are limitations in further reducing the size of the circuit portion 120 and it is difficult to reduce a chip size or costs.
In order to solve the above-mentioned problems of the related art, an object of the invention is to provide a semiconductor device which can reduce the size of a chip. In order to solve the above-mentioned problems of the related art, an object of the invention is to provide a semiconductor device which can reduce costs.